Battery-powered electrical device having a detachable battery pack

ABSTRACT

The battery pack used for the battery powered electrical device of the present invention comprises a case for accommodating at least two battery modules, a switching means provided on a side of the case, and an output terminal formed on the case. The switching means selectively closes and opens a series electrical connection of the at least two battery modules. The switching means cooperates with an actuator, which is provided on a side of a device&#39;s main body holding the battery pack detachably, to establish the series electrical connection when the case is attached to the device&#39;s main body, and to interrupt the series electrical connection when the case is detached from the device&#39;s main body.

TECHNICAL FIELD

This invention relates to a battery powered electrical device having adetachable battery pack.

BACKGROUND ART

A conventional battery pack for a battery powered electrical deviceincorporates a plurality of battery modules which are always connectedin series. The battery pack has an output terminal to output a totalvoltage of the battery modules connected in series to the outside of thebattery pack. When the battery pack is attached to a device's main body,the battery pack supplies electric power for the device's main bodythrough the output terminal, and drives the device's main body.

When the voltage outputted from the output terminal is on the order of10V, there are few problems, but when the voltage is on the order of100V, an electric shock may occur if a body touches the output terminal,or smoking or ignition may occur if a piece of metal touches the outputterminal.

DISCLOSURE OF THE INVENTION

In view of the above problem, the object of the present invention is toprovide a battery powered electrical device having a safety battery packwhich will never cause an electric shock or a short circuit even if abody or a piece of metal touches the output terminal.

The battery pack used for the battery powered electrical device of thepresent invention comprises a case for accommodating at least twobattery modules, a switching means provided on a side of the case, andan output terminal formed on the case. The switching means selectivelycloses and opens a series electrical connection of the at least twobattery modules. The switching means cooperates with an actuator, whichis provided on a side of a device's main body holding the battery packdetachably, to establish the series electrical connection when the caseis attached to the device's main body, and to interrupt the serieselectrical connection when the case is detached from the device's mainbody, i.e., when the actuator is detached from the case. The outputterminal is connected to an input terminal of the device's main body,and applies the series-connected voltage of the at least two batterymodules for the device's main body upon closing the switching means.

Therefore, this battery pack will never cause an electric shock or ashort circuit even if a body or a piece of metal touches the outputterminal when this battery pack is not attached to the device's mainbody; because the series electrical connection of the at least twobattery modules is interrupted then by opening the switching means. Onthe other hand, when this battery pack is attached to the device's mainbody, the switching means is forced to be closed, and the at least twobattery modules are connected in series, thereby allowing the outputterminal to supply electric power for the device's main body.

Preferably, the switching means has at least one pair of fixed contactsand a movable contact. The at least two battery modules have a positiveelectrode and a negative electrode, respectively, and the one pair offixed contacts is connected to the positive electrode of one of the atleast two battery modules and to the negative electrode of the other ofthe at least two battery modules, respectively. The movable contact ismovable between a closed position where the fixed contacts are connectedby the movable contact and an open position where the fixed contacts aredisconnected, and the movable contact is normally biased toward the openposition. The movable contact is disposed within an opening provided inthe case in an engageable relation with the actuator so that the movablecontact is forced to move into the closed position by the actuator whenthe actuator is inserted into the opening.

In this case, because the series electrical connection of the at leasttwo battery modules is established only when the actuator is insertedinto the opening, when the case is not attached to the device's mainbody, the series electrical connection of the at least two batterymodules is interrupted; therefore, there is no possibility of anelectric shock or a short circuit even if a body or a piece of metaltouches the output terminal.

Alternatively, it is also preferred that the switching means has atleast one pair of fixed electrodes. The case has a joint part forcoupling to the device's main body, and the fixed electrodes areconnected to the positive electrode of one of the at least two batterymodules and to the negative electrode of the other of the at least twobattery modules, respectively, and the fixed electrodes are disposed onthe joint part in spaced relation to each other. The actuator is in theform of a movable plate which is adapted to connect between the fixedelectrodes electrically when the joint part is coupled to the device'smain body.

In this case, because the series electrical connection of the at leasttwo battery modules is established only when the movable plateinterconnects the fixed electrodes, when the case is not attached to thedevice's main body, the series electrical connection of the at least twobattery modules is interrupted; therefore, there is no possibility of anelectric shock or a short circuit even if a body or a piece of metaltouches the output terminal.

If the switching means has at least two pairs of the fixed electrodes,it is preferred that each one pair of the fixed electrodes is disposedon each one of different faces of a polygon-shaped joint part. Each ofthe pairs of the fixed electrodes connect between the positive electrodeand the negative electrode of adjacent battery modules. The fixedelectrodes on the same face are disposed in spaced relation to eachother. The actuators are respectively in the form of a movable platewhich is adapted to interconnect between the fixed electrodes when thecase is physically coupled to the device's main body. Therefore, thisbattery pack will never cause an electric shock or a short circuit evenif a body or a piece of metal touches one face of the polygon-shapedjoint part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a battery powered electrical device inaccordance with a first embodiment of the present invention.

FIG. 2 is a view illustrating a battery powered electrical device inaccordance with a second embodiment of the present invention.

FIG. 3 is a view showing a preferred conformation of the secondembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail below withaccompanying drawings.

FIG. 1 shows a battery powered electrical device in accordance with afirst embodiment of the present invention. The battery poweredelectrical device comprises a device's main body 20 which has in itsinside an electrical driving source such as a large capacity motor, anda battery pack 1 which is held by the device's main body detachably andsupplies a large capacity power for the device's main body.

The battery pack 1 has eight battery modules A–H inside the case 2. Eachof the battery modules A–H comprises ten 1.2-volts battery cells 3connected in series, and outputs 12 volts. Each of the battery modulesA–H has a positive electrode p and a negative electrode n at both endsto output a series-connected voltage of 12 volts. A positive electrode pof a battery module A is electrically connected to a positive outputterminal P of an output terminal 8 protruding from one surface 2 a ofthe case 2, and a negative electrode n of a battery module H iselectrically connected to a negative output terminal N of the outputterminal 8. Except for the positive electrode p of the battery module Aand the negative electrode n of the battery module H, a negativeelectrode n of one of adjacent battery modules and a positive electrodep of the other of the adjacent battery modules are connected through aswitch 7. Each of the switches 7 selectively closes and opens a serieselectrical connection of adjacent battery modules. Each of the switches7 has one pair of fixed contacts 5, 5 and a movable contact 6. The fixedcontacts 5, 5 are connected to the negative electrode n of one ofadjacent battery modules and to the positive electrode of the other ofthe adjacent battery modules, respectively. Each of the movable contacts6 is movable between a closed position where the fixed contacts 5, 5 areconnected by the movable contact 6 and an open position where the fixedcontacts 5, 5 are disconnected, and is normally biased toward the openposition by a spring. When movable contact 6 of every switch 7 is in theclosed position, the battery modules A–H are electrically connected inseries, thereby allowing the battery pack to output a voltage of 96volts through the positive output terminal P and negative outputterminal N of the output terminal 8. The movable contacts 6 are disposedwithin seven openings 9 provided in the face 2 a of the case 2,respectively.

On a surface 20 a of the device's main body 20 to which the battery pack1 can be attached, column-shaped actuators 10 and an insertion hole 21are provided. The actuators 10 are formed at seven places correspondingto the openings 9 of the battery pack 1, respectively. On the inner wallof the insertion hole 21, input terminal 17, which is composed of apositive input terminal 17P and a negative input terminal 17N, isformed. Each of the actuators 10 will be inserted into the correspondingopening 9 when the battery pack is attached to the device's main body20. When the actuator 10 is inserted into the opening 9, the movablecontact 6 will be pushed by the actuator 10 and forced to move into theclosed position, thereby connecting adjacent battery modules in series.When the output terminal 8 is inserted, the positive input terminal 17Pand the negative input terminal 17N will contact the positive outputterminal P and the negative output terminal N of the output terminal 8,respectively. The device's main body 20 is driven by the power suppliedfrom the output terminal 8 of the battery pack 1 via the input terminal17.

Because the movable contact 6 is biased toward the open position, theseries electrical connection of the battery modules A–H is interruptedwhen the battery pack 1 is not attached to the device's main body 20;therefore, there is no possibility of an electric shock or a shortcircuit even if a body or a piece of metal touches the positive outputterminal P and negative output terminal N of the output terminal 8. Onthe other hand, when the battery pack 1 is attached to the device's mainbody 20, each of the actuators 10 is inserted into the opening 9, eachof the movable contacts 6 is forced to move into the closed position,and the battery modules A–H is connected in series, thereby allowing thebattery pack to apply the voltage of 96 volts from the positive outputterminal P and the negative output terminal N to the positive inputterminal 17P and the negative input terminal 17N. Because the positiveoutput terminal P and the negative output terminal N are inserted intothe insertion hole 21 while the battery pack 1 is attached to thedevice's main body, a user can not touch the positive output terminal Pand negative output terminal N; therefore there is no possibility of anelectric shock or a short circuit.

It should be noted that the battery pack 1 is held detachably to thedevice's main body by a well-known detachable mechanism. Although anexplanation about the detachable mechanism is omitted, the presentinvention can be applied to a device having the well-known detachablemechanism.

Each of the battery modules A–H is a battery module which can be chargedfrom the outside, and every battery modules can be replacedindividually.

FIG. 2 shows a battery pack in accordance with a second embodiment ofthe present invention. As is the case with the first embodiment, thebattery pack 1 has the eight battery modules A–H inside the case 2. Ajoint part 11, which is in the form of an octagon prism, is formed onthe surface 2 a of the case 2. An octagon-shaped insertion hole 22 intowhich the joint part 11 can be inserted is provided on the face 20 a ofthe device's main body 20 to which the battery pack 1 can be attached.The battery pack 1 is attached to the device's main body with the jointpart 11 inserted into the insertion hole 22.

On one external side surface out of eight external side surfaces of thejoint part 11, an output terminal 16 is formed, and on the sevenremaining external side surfaces, a switch 12 is formed, respectively.The output terminal 16 is composed of a positive electrode plate P and anegative electrode plate N, which are disposed in spaced relation toeach other. The positive electrode plate P is electrically connected tothe positive electrode p of the battery module A. The negative electrodeplate N is electrically connected to the negative electrode n of thebattery module H. Each of the switches 12 on each external side surfaceis composed of a pair of fixed electrodes 12 n, 12 p. The fixedelectrodes 12 n, 12 p is disposed in spaced relation to each other onthe same external side surface. The fixed electrode 12 n of each of thepairs of fixed electrodes 12 n, 12 p is electrically connected to anegative electrode n of one of certain adjacent battery modules, and thefixed electrode 12 p is electrically connected to a positive electrode pof the other of the adjacent battery modules. For example, one fixedelectrode 12 n of a certain pair of fixed electrodes 12 p, 12 n isconnected to the positive electrode p of the battery module A of theadjacent battery modules A, B, and the other fixed electrode 12 p isconnected to the negative electrode n of the other battery module B. Onefixed electrode 12 n of another pair of fixed electrodes 12 p, 12 n isconnected to the negative electrode n of the battery module B of theadjacent battery modules B, C, and the other fixed electrode 12 p isconnected to the positive electrode p of the other battery module C.

On one inner surface out of eight inner surfaces of the insertion hole22 of the device's main body 20, an input terminal 17 is formed, and onthe seven remaining inner surfaces, movable plates 13, as actuator, aredisposed, respectively. The input terminal 17 is composed of a positiveinput terminal 17P and a negative input terminal 17N. The positive inputterminal 17P and the negative input terminal 17N will contact thepositive output terminal P and the negative output terminal N of theoutput terminal 16, respectively, when the joint part 11 is insertedinto the insertion hole 22. When the joint part 11 is inserted into theinsertion hole 22, each of the movable plate 13 will contact both of thefixed electrodes 12 n, 12 p of the switch 12 which are disposed on onesurface of the joint part 11 and connect between the fixed electrodes 12n, 12 p. When all pairs of the fixed electrodes 12 n, 12 p are connectedby the movable plates 13, all battery modules A–H are connected inseries, thereby allowing the positive output terminal P and the negativeoutput terminal N of the output terminal 16 to output the voltage of 96volts.

Because the fixed contacts 12 n, 12 p are spaced to each other when thebattery pack is not attached to the device's main body 20, the serieselectrical connection of the battery modules A–H is interrupted then;therefore, the battery pack 1 configured as above can not cause anelectric shock or a short circuit even if a body or a piece of metaltouches the positive output terminal P and negative output terminal N ofthe output terminal 16. On the other hand, when the battery pack 1 isattached to the device's main body 20, each of the movable plates 13electrically connects between the fixed electrodes 12 n, 12 p, and allof the battery modules A–H are connected in series, thereby allowing theoutput terminal 16 to apply the voltage of 96 volts to the inputterminal 17 of the device's main body 20. Because the output terminal 16is inserted into the insertion hole 22 while the battery pack 1 isattached to the device's main body, a user can not touch the outputterminal 16; therefore there is no possibility of an electric shock or ashort circuit. Furthermore, because each of the pairs of the fixedelectrodes 12 n, 12 p is disposed on each surface of the joint part 11,the fixed electrode 12 n and the fixed electrode 12 p which areconnected to the negative electrode n and positive electrode p of thesame battery module, respectively, are disposed on different surfaces ofthe joint part 11. Therefore, even if a body or a piece of metal touchesone surface of the joint part 11, there is no possibility that onebattery module may cause a short circuit.

As shown in FIG. 3, eight LEDs 15 are disposed on one surface of thecase 2. The LEDs 15 are electrically connected to eight diagnosiscircuits 14, respectively, which are held inside the case 2. Thediagnosis circuits 14 are provided for each battery module A–H in orderto measure a voltage of each battery module. When the measured voltageis below a predetermined value, the diagnosis circuit 14 turns on acorresponding LED 15 and interrupts the series electrical connectionautomatically to stop the device. By stopping the device when abnormalbattery module is found, safety can be secured. The diagnosis circuit 14may interrupt the series electrical connection automatically to stop thedevice not only when the diagnosis circuit 14 finds the abnormal batterymodule but also when the diagnosis circuit 14 judges that the batterymodule is in the last stage from the measured voltage. In this case, areverse current (for example, when the battery module A finishes itsdischarge at an early stage, an electric current will flow into thebattery module A which has become a low voltage.) can be prevented,thereby not only securing the safety but also extending the life span.For this purpose, a fail-safe circuit is provided inside the batterypack. When the diagnosis circuit 14 detects that the voltage of thebattery module is below a predetermined value or the voltage is in thelast stage, the diagnosis circuit 14 will generate an error signal, andin response to the error signal, the fail-safe circuit will turn on thecorresponding LED and interrupt the series electrical connection of thebattery pack by a switching means.

1. A battery powered electrical device composed of a battery pack and adevice's main body detachably holding said battery pack to be poweredthereby, said device comprising: a case provided in said battery packfor accommodating at least two battery modules each comprising aplurality of battery cells connected in series; a switching meansprovided on a side of said case, said switching means selectivelyclosing and opening a series electrical connection of said at least twobattery modules, an output terminal formed on said case, said outputterminal applying a series-connected voltage of said at least twobattery modules to said device's main body upon closing said switchingmeans, an actuator provided on a side of said device's main body,wherein said switching means is provided on an electric pathway betweensaid at least two battery modules, and cooperates with said actuator toestablish said series electrical connection when said case is attachedto said device's main body, and to interrupt said series electricalconnection when said actuator is detached from said case.
 2. The batterypowered electrical device as set forth in claim 1, wherein each of saidat least two battery modules has a positive electrode and a negativeelectrode, said switching means having at least one pair of fixedcontacts and a movable contact, said fixed contacts being connected tothe positive electrode of one of said at least two battery modules andto the negative electrode of the other of said at least two batterymodules, respectively, said movable contact being movable between aclosed position where said fixed contacts are connected by the movablecontact and an open position where said fixed contacts are disconnected,said movable contact being normally biased toward the open position,said movable contact being disposed within an opening provided in saidcase in an engageable relation with said actuator so that said movablecontact is forced to move into said closed position by said actuatorwhen the actuator is inserted into said opening.
 3. The battery poweredelectrical device as set forth in claim 1, wherein said case has a jointpart for coupling to said device's main body, each of said at least twobattery modules having a positive electrode and a negative electrode,said switching means having at least one pair of fixed electrodes, saidfixed electrodes being connected to the positive electrode of one ofsaid at least two battery modules and to the negative electrode of theother of said at least two battery modules, respectively, said fixedelectrodes being disposed on said joint part in spaced relation to eachother, said actuator being in the form of a movable plate whichinterconnects said fixed electrodes electrically when said joint part iscoupled to said device's main body.
 4. A battery powered electricaldevice composed of a battery pack and a device's main body detachablyholding said battery pack to be powered thereby, said device comprising:a case provided in said battery pack for accommodating at least threebattery modules; a switching means providing on a side of said case,said switching means selectively closing and opening a series electricalconnection of said at least three battery modules, an output terminalformed on said case, said output terminal applying a series-connectedvoltage of said at least three battery modules to said device's mainbody upon said switching means being closed, actuators provided on aside of said device's main body, wherein said case has a polygon-shapedjoint part for coupling to said device's main body, each of said atleast three battery modules having a positive electrode and a negativeelectrode, said switching means having at least two pairs of fixedelectrodes, said fixed electrodes being provided for electricalconnection between said positive electrode and said negative electrodeof adjacent battery modules, said each one pair of the fixed electrodesbeing disposed on each one of different faces of said polygon-shapedjoint part, said fixed electrodes in said each pair on the same facebeing disposed in spaced relation to each other, each of said actuatorsbeing in the form of a movable plate which interconnects between saidone pair of the fixed electrodes when said case is physically coupled tosaid device's main body.